1. Field of the Invention
The present invention relates to a unexpanded perlite ore polishing composition and method for polishing selected materials wherein an unexpanded perlite ore composition having grains of a selected distribution of particle sizes resulting in continued fracturing of the grains subject to an abrasive force applied to the composition during polishing. This results in an increase in the number of grains of unexpanded perlite ore having a smaller particle size than the selected distribution of particle sizes for efficient polishing and more particularly relates to a unexpanded perlite ore polishing composition and method for selectively abrading and polishing polymers, including acrylic polymers, dentures and other parts, components and articles fabricated from materials suitable for polishing with unexpanded perlite ore including optical glass, lenses and cathode ray tubes (CRT) surfaces subject to an abrasive force.
2. Description of the Prior Art
It is known in the art to use granular compositions for abrasion and polishing of the surfaces of an article.
Certain applications utilize pumice as an abrasive material or as an abrasive material additive to a polishing composition. Pumice is a rock froth formed by the extreme puffing of liquid lava by expanding gases liberated from solution in the lava prior to and during solidification. Pumice and pumicite are porous, glassy forms of lava, rich in silica. Both plumice, the massive form, and pumicite, the powder or dust form, have been widely used as a mild abrasive for polishing operations.
FIGS. 1 and 2 labeled “Prior Art” are scanning electron micrographs of pumice grains at magnifications of 100× and 300×, respectively. As depicted in the micrographs of FIGS. 1 and 2, the grains or particles of pumice have a plurality of large pores, or more specifically vesicles, that are an essential part to the definition of rock type. The large pores are separated by a plurality of substantially parallel planes with sharp edges or strata defining the structure thereof. The pumice, when used as an abrasive in a polishing material, typically generates scratches which is generally undesirable. The scratches are formed in the surface of an article by the aforementioned sharp edges of the pumice grains. Scratches generally require additional polishing using a fine polishing composition to remove the same and to polish the surface of the article to the desired finish.
A polish composition and method of use which utilizes suitable mild abrasives, such as pumice, are disclosed in U.S. Pat. No. 6,235,824.
It is also known in the art to use abrasive material in combination with individual grains of pumice in coated abrasive articles comprised of a backing having a layer of grains adherently bonded thereto by a binding material, an example of which is disclosed in U.S. Pat. No. 5,840,090.
It is also known in the art to have a granular composition which utilizes pumice as a part thereof, an example of which is disclosed in U.S. Pat. No. 5,891,473.
It also known in the art that toothpaste can be formulated to include a lightweight, low density solid filler such as expanded perlite as disclosed in U.S. Pat. No. 6,139,820.
It is also known in the art to utilize low-density expanded perlite as an abrasive in toothpaste as disclosed in U.S. Pat. No. 5,597,553. Specifically, U.S. Pat. No. 5,597,553 discloses a specific use of an expanded perlite in toothpaste which disintegrates when subjected to small mechanical stress, e.g., under the conditions of tooth brushing, into smaller, sharp-edged particles and that the same are well suited as a cleaning body in the toothpaste. U.S. Pat. No. 5,597,553 further discloses that the relatively course particles of expanded perlite have a size of the order of about 1 μm to 150 μm, the major portion being of about 20 μm. The expanded perlite particles are disclosed as performing a very short-lasting, but intensive cleaning action and are immediately comminuted into still finer particles which then perform a desired, mild polishing action down to a fine polishing. In U.S. Pat. No. 5,597,553, the specification recites that only the exploded (expanded) perlite is used in the toothpaste disclosed therein.
Toothpastes utilizing an expanded perlite are also disclosed in U.S. Pat. Nos. 5,597,553 and 5,124,143.
It is also known in the art to utilize exploded (expanded) perlite in a water-free prophylectic paste containing expanded perlite as disclosed in U.S. Pat. No. 6,139,820.
It is also known in the art that a cleaning composition containing a type II endoglycosidase includes an expanded perlite abrasive as a part thereof as disclosed in U.S. Pat. No. 5,395,541.
It is also known in the art to use a blend of polishing and cleaning agents in a prophylaxis procedure for stain removal and polishing of teeth. Such a blend of polishing and cleaning agents are generally known as prophy paste and may include fluoride ions. Certain of the known prophy paste use expanded perlite and pumice as grit material in the prophy paste. Examples of prophy paste using expanded perlite and pumice are the 3M brand prophy pastes known as 3M™ CLINPRO™ prophy paste and NUPRO® brand prophy paste sold by DENTSPLY. Other known prophy paste products are sold by WhiteHill Manufacturing, Inc. under the trademark Professional Prophy Products.
It is also known to incorporate “soft abrasive” polish into dental floss and dental tape, and such products are sold by WhiteHill Manufacturing, Inc. under the trademark Professional Prophy Products.
An oral prophalaxis paste which includes a preselected grade and amount of abrasive material such as pumice, clay or diatimoceous earth is disclosed in U.S. Pat. No. 6,280,707.
It is also known in the art to utilize pumice as an abrasive material for polishing a CRT glass panel wherein the polishing thereof is conducted in the presence of the abrasive material including the pumice in a state of slurry. In polishing CRT glass panels, the polishing pressures are in a range of about 0.2 kg/cm2 (200 kg/cm2) to 2.0 kg/cm2 (2000 kg/cm2), more preferably in the range of about 0.4 kg/cm2 (400 kg/cm2) to about 1.2 kg/cm2 (1200 kg/cm2). Generally, when the abrasive or polishing force is less than about 0.2 kg/cm2 (200 kg/cm2), the abrasive or polishing force is usually insufficient and the efficiently of the polishing is reduced. Further, it is known to use multiple grades of pumice to affect the polishing process. Typically, a coarse grade pumice is first used in the polishing process to polish the surface of a CRT which is then followed by polishing using a medium grade pumice.
It is also known to use only a single grade of pumice, typically a finer grade, for polishing a CRT surface and to then use a final polishing operation that employs a cerium oxide to obtain the desired polished surface.
Polishes are used to maintain a glossy finish or sheen on surfaces as well as to prolong the useful lives of these surfaces. Appearance enhancement provided by polishes generally results from materials that smooth and clean surfaces through abrasive action, or leave a glossy coating, or both. A description of polishes and uses thereof are set forth at pages 444 through 453 in the Kirk-Othmer Encyclopedia of Chemical Technology, John Wiley & Sons, 1996, 4th Edition, Vol. 19) (the “Chemical Technology, Vol. 19 Reference”). The Chemical Technology, Vol. 19 Reference is incorporated herein by reference.
Many materials have been used as abrasives, usually in one of three forms in polishing operations: grit (loose, granular, or powdered particles); bonded materials (particles are bonded into wheels, segments, or stick shapes); and coated materials (particles are bonded to paper, plastic, cloth, or metal). Grit is often useful for polishing, buffing, lapping, pressure blasting, barrel finishing, jet cutting, and high-pressure jet cutting. Natural abrasives of commercial significance include diamond, corundum, emery, garnet, silica, sandstone, tripoli, pumice, and pumicite, and to a lesser extent, powdered feldspar and staurolite. A description of abrasives and uses thereof are set forth at pages 17 through 37 of the Kirk-Othmer Encyclopedia of Chemical Technology, John Wiley & Sons, 1991, 4th Edition, Vol. 1 (the “Chemical Technology, Vol. 1 Reference”). The Chemical Technology, Vol. 1 Reference is incorporated by reference.
Other known Natural Glasses and Macerals are disclosed and described in Appendix A, Natural Glasses and Macerals, page 540 through 542, in Mineralogy, W. H. Freeman and Company, 2nd Edition (the “Mineralogy Reference”). The Mineralogy Reference is incorporated by reference.
Materials including Thermoplastic materials and thermoset materials generally recognized as “engineering materials”, including acrylic polymers, are disclosed and described at pages 371 through 511 of The Handbook of Industrial Materials, Elsevier Advanced Technology, 2nd Edition (the “Industrial Materials Reference”). The Industrial Materials Reference is incorporated by reference herein.
Glasses comprise a wide variety of vitreous amorphous polymers consisting of repeating siloxane (i.e., —(Si—O)—) units in the polymer chain. Some glasses are naturally occurring, such as perlite. Others, such as soda-lime glasses, are produced synthetically. Soda-lime glass is made by melting batches of raw materials containing the oxides of silicon (i.e., SiO2), aluminum (i.e., Al2O3), calcium (i.e., CaO), sodium (i.e., Na2O), and sometimes potassium (i.e., K2O), or lithium (i.e., Li2O) together in a furnace, and then allowing the melt to cool so as to produce the amorphous product. Glasses may be made in a wide variety of shapes, including sheets or plates, cast shapes, or fibers. Often, glass is not sufficiently smooth as first produced, for the intended end use, and requires further polishing.
Among the glasses requiring polishing for final use include cathode ray tubes and television tubes, eyeglasses, photographic optical components, and laser optical components. These glasses are prepared in a wide array of chemical compositions, and thus have various hardnesses and physical properties. Being a natural glass itself, the unexpanded perlite ore polishing composition is useful for polishing glasses, provided the glass is equal to or less than the hardness of the unexpanded perlite ore polishing composition.
It is also known in the art to etch or polishing a surface of an article using a method and apparatus for blowing an airstream containing use submicron particles thereacross. One example of a surface process method by blowing submicron particles is disclosed in U.S. Pat. No. 5,928,719.
Principles of grinding and polishing of materials, such as plastics and polymers, including the use of grinding, hand polishing and automated polishing systems are described in Pages 1 through 10 of the STANDARD GUIDE FOR PREPARATION OF PLASTICS AND POLYMERIC SPECIMENS FOR MICROSTRUCTURAL EXAMINATION, Designation: E 2015-99, American Society for Testing and Materials (the “ASTM Standard Guide Reference”). The ATSM Standard Guide Reference in Section 11 captioned “Polishing” sets forth information relating to rough polishing and fine or final polishing. ATSM Standard Guide Reference includes methods for measuring flatness of a polished surface, typical applied pressures to obtain the desired polishing and effective wheel speeds for automated polishing. The disclosures set forth in the ATSM Standard Guide Reference can be used in practicing this invention.
The rate at which the final polishing of a surface can be obtained using the unexpanded perlite ore composition of the present invention can be by microscopical analysis by reflected light.
For example, if the selected distribution of selected sizes of the grains of unexpanded perlite ore composition have a (d90) having a larger particle size, e.g. greater than 245 μm, then the rate at which the unexpanded perlite ore composition comminutes or fractures will be higher which is desirable for a higher level of coarse polishing. On the other hand, if the selected distribution of selected sizes of the grains of unexpanded perlite ore composition have a (d90) having a smaller particle size, e.g. about 100 μm, then the rate at which the unexpanded perlite ore composition comminutes or fractures will lower which is desirable for a fine polish level.
It is envisioned that measurements of rates of effective coarse polishing and fine polishing can be determined by microscopical analysis of a polished surface using reflected light in a manner similar to the method described in Pages 1 through 4 of the STANDARD PRACTICE GUIDE FOR PREPARING COAL SAMPLES FOR MICROSCOPICAL ANALYSIS BY REFLECTED LIGHT, Designation: D2797-85 Reapproved 1999), American Society for Testing and Materials (the “ASTM Microscopical Analysis Reference”). The ATSM Microscopical Analysis Reference in Section 9 captioned “Preparation of Briquet Surface” sets forth information relating to grinding and polishing of a briquet on a lap to obtain a surface suitable for microscopic examination. The same method can be used to determine the effectiveness of both coarse polishing and fine polishing of a desired surface.
The disclosure of all of the above references and Patents and other references referred into this specification are hereby incorporated by reference as if set forth verbatim herein.